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Fri May 26 15:30:38 UTC 2017
In my understanding, humidity should be nearly equivalent between cyan and pt/pd. (I have a limited understanding of Cyanotype but this was what we did at MM Workshops.)
HPR is especially sensitive to humidity and I recommend no less than 45% and no more than 66% and also to make sure your temperature is under 74 degrees F. High humidity and high temperature can result in issues with this paper.
Low humidity and result in even more issues though (streaking, etc). This paper also needs specific amounts of Tween20 or PhotoFlo (surfactants) or the solution will not go in properly.
All in all, the variables must be tested in a scientific way before optimal conditions are met.
> On May 26, 2017, at 11:02 AM, Bob Cornelis via Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org> wrote:
> I've looked through all the cyanotype docs on Mike Ware's site and haven't
> found anything addressing my question about specific humidity
> guidelines/recommendations for Ware cyanotype, hopefully I just didn't
> overlook it. Took a more cursory look for pt/pd info but it seems most of
> that on the site pertains to some revisions Mike has made to that process -
> not sure it would pertain to the classic formula even if there was specific
> humidity info (which I also didn't see).
> So I'm still open to input from anyone out there who has come to some
> conclusions about this. Is there a range within which you want to try to
> stay? I know some people resort to humidifiers and de-humidifiers to
> maintain certain levels, don't want to do this if I'm in the "safe zone",
> but open to it if I'm not and it matters much.
> With my pt/pd work I was taught to dry the coated paper to somewhat less
> than bone dry (as opposed to cyanotype). I'm thinking that this is meant to
> address the sensitivity to that process to humidity. But my methodology for
> that is not very precise.
> One reason I'm interested is that I'm suddenly getting radically different
> (and strange) results with cyanotype on HPR in terms of how the coating is
> behaving - only difference in workflow is that the humidity has gone up
> about 10% in my studio since last time I worked (from 50% to 60%). Still
> testing what might be going on there.
> On Thu, May 25, 2017 at 11:44 AM, Keith Schreiber via
> Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org>
>> Not off the top of my head, but Mike has a lot of information on his
>> website <http://www.mikeware.co.uk/mikeware/main.html>. I'm sure you can
>> find it there.
>> Keith Schreiber
>>> On May 25, 2017, at 12:26 PM, Bob Cornelis via Alt-photo-process-list <
>> alt-photo-process-list at lists.altphotolist.org> wrote:
>>> Does anyone know what the recommended humidity range is for
>>> 1) cyanotype (Ware)
>>> 2) pt/pd
>>> I haven't found any specific info like this in any of my alt process
>>> just general comments that humidity makes a difference.
>>> Alt-photo-process-list | altphotolist.org
>> Alt-photo-process-list | altphotolist.org
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